In recent years, a broadband communication line such as the ADSL (Asymmetric Digital Subscriber Line) or the like capable of performing high-speed data transmission is in widespread use. Here, the ADSL is characterized by using the same metallic cable as the existing subscriber's line, whereby the identical line can be used for both an analog telephone service and a network connection service. That is, it is possible by inserting a frequency division filter called a splitter between the communication line and a communication terminal to separate the line for transmitting a voice band signal and the line for transmitting digital data from each other.
Incidentally, when the above line is used for the analog telephone service, various configurations such as “ADSL modem+splitter+computer”, “ADSL modem+splitter+router”, and the like are conceivable as combinations of subscriber's devices. Moreover, for example, the configuration which integrally includes the ADSL modem and the splitter is conceivable as an ADSL gateway which takes account of sharing with a telephone.
The ADSL gateway like this is equipped with a modular jack so as to be able to connect the analog telephone to, e.g., the line for transmitting the voice band signal. Thus, a communication apparatus such as a telephone, a facsimile machine or the like is connected to the modular jack, whereby communication can be performed by means of the connected communication apparatus.
Moreover, the ADSL gateway like this is equipped with a connection interface of CSMA/CD (Carrier Sense Multiple Access with Collision Detection) such as Ethernet™ or the like so as to achieve high-speed digital communication. Thus, it is possible by connecting a PC (personal computer) or the like to such a CSMA/CD interface to be able to download various data at high speed from, e.g., a WWW (World Wide Web) server. Here, it should be noted that, in addition to the CSMA/CD interface, another interface such as USB (Universal Serial Bus) or the like is also used as the interface between the ADSL gateway and a network device such as a PC.
The terminal such as the PC which is connected to the server and thus used can achieve high-speed communication. However, the terminal such as the telephone, the facsimile machine or the like which performs data exchange in real time to a communication partner terminal through a line exchange network (i.e., an analog communication path) generally uses an analog band. Here, in an analog facsimile procedure, although any problem does not occur when binary (i.e., black and white) image data or the like is transmitted, a problem that a long communication time is necessary occurs when large-capacity color image data (according to a JPEG (Joint Photographic Experts Group) format or the like) obtained by means of a digital camera or the like is transmitted.
In order to be able to transmit communication data such as image data or the like at high speed, a procedure to connect the facsimile machine to the CSMA/CD interface, upload a packet of the image data to a file server (for example, by using a protocol such as FTP (File Transfer Protocol), HTTP (HyperText Transfer Protocol) or the like), and then download the packet data from the file server to a communication partner terminal is necessary. However, in that case, there is a problem that the communication partner terminal (i.e., a reception side) has to take the trouble to access the server for receiving the image data, and there is also a problem that real-time communication cannot be performed. Moreover, when a destination address on the reception side is notified to the server, or when the data is downloaded on the initiative of the reception side, a mechanism for notifying the reception side of data upload is necessary. In other words, it is difficult in that case to achieve data communication by a simple operation as in the conventional facsimile machine of only setting a mere communication partner's telephone number.
In consideration of the above point, Japanese Patent Application Laid-Open No. H10-107938 (called a document 1 hereinafter) discloses that image communication is performed through a server on an IP network. More specifically, in this document, a first terminal on an image transmission side calls a server concerning the first terminal, the first terminal is connected to a computer network through the called server concerning the first terminal, a second terminal being an image reception side is designated, a network server concerning the second terminal calls the second terminal, the first terminal transmits image data to the server concerning the second terminal through the computer network in the form suitable for the computer network, the server concerning the second terminal converts the received image data of the form suitable for the computer network into facsimile image, the server concerning the second terminal transmits the obtained facsimile image data to the second terminal through a public line, and the second terminal actually reproduces an image from the received facsimile image data.
Moreover, Japanese Patent Application Laid-Open No. H09-247334 (called a document 2 hereinafter), Japanese Patent Application Laid-Open No. H10-133967 (called a document 3 hereinafter), and the like propose various kinds of methods of transmitting an image in the form of an electronic mail by inputting an Internet address of a transmission destination.
Furthermore, Japanese Patent Application Laid-Open No. 2000-354127 (called a document 4 hereinafter), Japanese Patent Application Laid-Open No. 2001-197279 (called a document 5 hereinafter), and the like propose various kinds of methods of relaying facsimile image transmission on the Internet in real time by applying a protocol based on ITU-T (International Telecommunication Union Telecommunication Standardization Sector) Recommendation. T.38.
However, in the document 1, it is necessary for the transmission-source terminal to dial-up access to the server, perform a log-in process including an authentication procedure and the like, and further input the telephone number of the transmission-destination terminal. That is, it is impossible to easily perform image transmission only by inputting a destination's telephone number as in the conventional facsimile machine.
Moreover, in the documents 2 and 3, when the image is transmitted through the Internet, it is necessary for the transmission source side to input a mail address of the transmission destination at the reception side. Furthermore, to transmit the image in the form of the electronic mail, image data representing the image in question is once stored in a server, and it is then necessary for the reception side to access the server according to an electronic mail reading protocol such as POP (Post Office Profile) or the like and actually receive the image data.
In addition, in the documents 4 and 5, it is necessary to provide a dedicated gateway for the protocol based on ITU-T Recommendation T.38. Meanwhile, in these documents, because the ordinary telephone line is used between the terminal and the Internet, the obtained transmission speed is the same as that in the facsimile communication using the conventional line switching network.